This invention relates to methods of stimulating electrically excitable living tissue, e.g., nerves and muscle fibers, and is considered particularly applicable to tissues that demonstrate functional variation with location, such as the tonotopic variation of the spiral ganglia of the auditory nerve, and the spatial variation of motor nerves within the spinal cord.
Within excitable tissue, especially neurons, individual neighboring cells could correspond to functionally unique tasks. In some applications, this results in a high level of resolution within a region of cells. Sensory organs commonly express this type of resolution. For example, the cochlea consists of a helical region of excitable tissue that relates to a mapping of sensed sound frequency from one end to another, and neighboring cells within this region may relate to appreciably different frequencies. Existing technology either creates a specific point of stimulation without the ability to change the location (except for physical adjustment, e.g., electrodes), or has some adjustability but creates a very broad region of stimulation (e.g., magnetic field stimulation). A need exists for technology capable of providing a high degree of stimulation resolution as well as the ability to focus the stimulation at any desired location.